Multi-carrier modulation techniques, such as orthogonal frequency division multiplexing (OFDM), have become widely used in high-speed wireless communications. By partitioning a wideband fading channel into narrowband channels, OFDM is able to mitigate the detrimental transmission effects such as multipath fading. However, in the time domain OFDM signals suffer from a high peak-to-average power ratio (PAPR).
The OFDM waveform is the result of the cancellation and accumulation of waveform symbols transmitted in different frequency channels. When the phases of several waveform symbols align, the combined waveform has a large peak. To prevent distortion of the combined waveform by the transmitting radio frequency (RF) power amplifier, the RF power amplifier should have high linearity, including high linearity at the peak transmit power. The gain of the RF power amplifier is generally set to achieve the high linearity at the peak transmit power, and this reduces the average transmit power for a waveform with a high PAPR. The reduced average transmit power reduces the transmitted signal, and hence the signal to noise ratio (SNR).
The disclosed embodiments may address one or more of the above issues.